Which will be better? This HD 7850 4gb or any other 7870 Brands. They're almost the same price and im looking for a better gaming performance in 1920x1080 or 1680x1050 resolutions. And what modular PSU will be good for it under 90$.
The HD 7870 XT is very close to the HD 7950. And the SeaSonic 520W is sufficient. You don't need 600W or more.
Is 7950 worth it for 20-50$ difference against 7870? Im getting FX 8320 CPU, Is 520W still enough if i add 6+ case fans, fan controller, LED strip, additional PCIe cards and doing CrossfireX about a year?
For CrossFireX, I would get a XFX 650W PSU. Also, fans, fan controller, and LED strips use negligible power. As for additional PCIe cards, you'll have to be more specific. You can always get a Corsair TX750 V2 PSU, but that would be total overkill and a waste of money if you don't need that much power.